Process and device for detecting the failure of a pressure sensor of an air data system of an aircraft

ABSTRACT

Process and device for detecting the failure of a pressure sensor of an air data system of an aircraft.  
     The device ( 1 ) for detecting the failure of a process sensor ( 5 ) of an air data system ( 2 ) of an aircraft comprising at least two pressure sensors ( 5 ), comprises means for acquiring the values of measurements made by the pressure sensors ( 5 ), means for calculating the deviation between the values thus measured, means for comparing this deviation with a predetermined threshold value, and means ( 13 ) for displaying, if said deviation is greater than said threshold value, a failure cue relating to the air data system ( 2 ) on a display device ( 15 ) which is mounted on the aircraft.

[0001] The present invention relates to a process and a device fordetecting the failure of a pressure sensor of an air data system of anaircraft, which comprises at least two pressure sensors.

[0002] It is known that such an air data system is intended formeasuring air data making it possible to determine values of parameterssuch as the altitude of the aircraft, its speed, etc. For this purpose,said air data system comprises pressure sensors that are connected bytubes to probes that pass through the fuselage of the aircraft.

[0003] Generally, a civil transport airplane comprises three air datasystems of this type, of which:

[0004] a first provides data which are displayed in the cockpit, for theattention of the pilot;

[0005] a second provides data which are also displayed in the cockpit,but for the attention of the co-pilot; and

[0006] a third is used as backup to cope if necessary with the failureof one of said first two systems.

[0007] For obvious safety reasons, these three air data systems must bemade and must operate in a manner which is completely independent of oneanother, since otherwise the failure of one would have repercussions onthe measurements of the other systems.

[0008] Moreover, it is known that human errors, in particular duringairplane maintenance operations, may give rise to the failure of one ormore of the pressure sensors of such an air data system.

[0009] For example, the personnel in charge of performing an operationof washing the airplane frequently stick a piece of adhesive tape ontoeach of the probes of the air data system, so as to prevent water frompenetrating into the tube during said washing. If they forget to removeone of said pieces of adhesive tape after the washing, the correspondingpressure sensor will fail during the next flight of the airplane, sinceit will be unable to measure the pressure of the air outside thefuselage. It will in fact measure the pressure of the air in the tubewhich is closed, at its end on the probe side, by the adhesive piece.

[0010] Another exemplary failure relates to the case where maintenancepersonnel disconnect the tube and the pressure sensor at the level of anappropriate connector, so as for example to clean the inside of thistube. If they forget to reconnect the tube to the pressure sensor aftercarrying out the maintenance operation, said pressure sensor will alsofail, since it will measure the pressure of the air inside the fuselageinstead of measuring the pressure of the air outside the fuselage.

[0011] The object of the present invention is to remedy these drawbacks.It relates to a process for detecting, in a rapid and reliable manner,and at a reduced cost, the failure of a pressure sensor of an air datasystem of an aircraft, which comprises at least two pressure sensors.

[0012] For this purpose, said process is noteworthy, according to theinvention, in that at least the following first series of steps iscarried out:

[0013] A1) pressure measurements are made with the aid of said twopressure sensors so as to obtain, respectively, first and secondpressure values;

[0014] A2) the deviation between said first and second pressure valuesis calculated;

[0015] A3) this deviation is compared with a predetermined thresholdvalue, for example 30 mbar; and

[0016] A4) if said deviation is greater than said threshold value, afailure cue relating to said air data system is displayed on a displaydevice which is mounted on said aircraft.

[0017] Thus, by virtue of said first series of steps A1) to A4), anyfailure of a pressure sensor of an air data system can be rapidly andreliably detected, without calling upon information external to this airdata system, such as for example information output by other air datasystems of the aircraft. This therefore makes it possible, should aplurality of air data systems be present on the aircraft, to guaranteethe strict mutual independence of the various air data systems of theaircraft.

[0018] Advantageously, the following steps are moreover carried out:

[0019] the speed of the aircraft relative to the air is measured in sucha way as to obtain an air speed value;

[0020] the air speed value thus measured is compared with apredetermined speed threshold; and

[0021] a failure cue is displayed in step A4), [of the aforesaid firstseries of steps A1) to A4)] only if said air speed value is greater thansaid speed threshold.

[0022] This has the advantage that a failure of said air data system isnot signaled in an untimely manner when the aircraft is subjected on theground to a side wind causing a considerable difference between thepressures measured by the pressure sensors situated at different placeson the fuselage, in particular in the right part and in the left part ofthe fuselage. This predetermined speed threshold, for example 25 m/s(around 50 knots), is chosen, preferably, so that the effect of a sidewind corresponding to a wind of maximum intensity does not give rise tothe unjustified signaling of a failure during takeoff of the aircraft.

[0023] Furthermore, in a particular implementation:

[0024] at least three pressure sensors are provided for said air datasystem;

[0025] in step A1), pressure measurements are made with the aid of saidthree pressure sensors;

[0026] in step A2), all the possible deviations between the variouspressure values taken pairwise are calculated,

[0027] in step A3), all the deviations thus calculated are compared withsaid threshold value; and

[0028] in step A4), a failure cue is or is not displayed depending onthe various comparisons thus carried out.

[0029] More precisely, in said step A4), a failure cue is displayed:

[0030] in a first variant, if at least one of said deviations is greaterthan said threshold value; and

[0031] in a second variant, only if all the deviations are greater thansaid threshold value.

[0032] Moreover, the process in accordance with the invention is alsonoteworthy in that at least the following second series of steps ismoreover carried out:

[0033] B1) pressure measurements are made with the aid of at least onepressure sensor of the air data system, on the aircraft which is on theground and the cabin of which is not pressurized, so as to obtain athird pressure value;

[0034] B2) on the basis of this third pressure value, a first altitudecorresponding to the ground altitude is calculated;

[0035] B3) the cabin of the aircraft is pressurized;

[0036] B4) the aircraft is made to take off;

[0037] B5) at a predetermined time after takeoff, pressure measurementsare made with the aid of said pressure sensor so as to obtain a fourthpressure value;

[0038] B6) on the basis of this fourth pressure value, a second altitudecorresponding to the aircraft's altitude is calculated at the aforesaidinstant;

[0039] B7) a third altitude corresponding to the aircraft's altitudewith respect to the ground is calculated, from said first and secondaltitudes;

[0040] B8) said third altitude is compared with a predetermined altitudethreshold; and

[0041] B9) if said third altitude is less than said predeterminedaltitude threshold, a failure cue relating to said air data system isdisplayed on a display device which is mounted on said aircraft.

[0042] This second series of steps B1) to B9) has the advantage ofallowing the detection of the simultaneous failure of several pressuresensors of one and the same air data system. It may for example bedeployed by an alarm signaling/monitoring facility provided on theaircraft.

[0043] Furthermore, advantageously, in the case of an aircraft fittedwith at least two engines, said altitude threshold is less than thealtitude reached by the aircraft, at said predetermined time aftertakeoff, should there be a fault with at least one of said engines. Inthis case, preferably, said predetermined time after takeoff issubstantially equal to 30 seconds, and said altitude threshold issubstantially equal to 30 meters (around 100 feet). Moreover,advantageously, the following steps are moreover carried out:

[0044] the operation of the engines of the aircraft is monitored; and

[0045] when a malfunction of at least one of the engines of the aircraftis detected, a failure cue is not displayed if appropriate in theaforesaid step B9).

[0046] The process in accordance with the invention is also noteworthyin that at least the following third series of steps is moreover carriedout:

[0047] C1) at least one detector which is able to detect a failedcoupling between the corresponding pressure sensor and a probe of saidair data system, which is associated with this pressure sensor, isprovided on at least some of the pressure sensors;

[0048] C2) the acquisition on the ground, before takeoff, of cuesrelating to said coupling, which emanate from said detectors, is carriedout; and

[0049] C3) if at least one of said detectors signals a failed coupling,a failure cue relating to said air data system is displayed on a displaydevice which is mounted on the aircraft.

[0050] Preferably, at least one of said detectors is integrated into apneumatic connector intended to join a pneumatic tube associated with aprobe to the corresponding pressure sensor.

[0051] The present invention also relates to a device for detecting thefailure of a pressure sensor of an air data system of an aircraft, whichcomprises at least two pressure sensors.

[0052] According to the invention, said device is noteworthy in that itcomprises:

[0053] means for acquiring the values of measurements made by saidpressure sensors;

[0054] means of calculation;

[0055] means of comparison;

[0056] means of selection; and

[0057] means of display able to display, on at least one display devicewhich is mounted on said aircraft, a failure cue relating to said airdata system.

[0058] The figures of the appended drawing will elucidate the manner inwhich the invention may be implemented. In these figures, identicalreferences designate similar elements.

[0059]FIG. 1 is the schematic diagram of a device in accordance with theinvention.

[0060]FIGS. 2 and 3 diagrammatically illustrate different modes ofimplementation of a central unit of a device in accordance with theinvention.

[0061]FIGS. 4 and 5 diagrammatically illustrate complementary elementsof a central unit of a device in accordance with the invention.

[0062] The device 1 in accordance with the invention and representeddiagrammatically in FIG. 1 is intended for monitoring a standard airdata system 2 of an aircraft, in particular of a civil transportairplane, of which only a part of the fuselage 3 has been represented inthis FIG. 1 for reasons of simplification of the drawing.

[0063] It is known that such an air data system 2 is intended formeasuring air data making it possible to determine values of parameterssuch as the altitude, the speed, etc., of the aircraft. To do this, theair data system 2 comprises, in a known manner:

[0064] probes 4 which are mounted, in a feed-through manner, on thefuselage 3 of the aircraft and access the exterior;

[0065] pressure sensors 5 which are each connected by way of a tube 6 toa probe 4. Generally, such a tube 6 which effects a pneumatic link isconnected to the associated pressure sensor 5 by means of a pneumaticconnector 7 which makes it possible to disconnect it and reconnect iteasily and rapidly. Moreover, with each pressure sensor 5 is associatedan analog/digital converter 8; and

[0066] a central unit 11 which is connected to the pressure sensors 5 byelectrical links 12, for example in the form of a communication buscomplying with the “ARINC 429” standard.

[0067] It is however also conceivable to integrate the pressure sensors5 into the central unit 11.

[0068] Generally, a civil transport airplane comprises three air datasystems 2 of this type, of which:

[0069] a first provides data which are displayed in the cockpit, for theattention of the pilot;

[0070] a second provides data which are also displayed in the cockpit,but for the attention of the co-pilot; and

[0071] a third is used as backup to cope if necessary with the failureof one of said first and second systems.

[0072] For obvious safety reasons, these three air data systems must bemade and must operate in a manner which is completely independent of oneanother, since otherwise the failure of one would have repercussions onthe measurements of the other systems.

[0073] An object of the device 1 in accordance with the invention is todetect any failure of a pressure sensor 5 of such an air data system 2.

[0074] For this purpose, said device 1 comprises:

[0075] said central unit 11 which is such as specified hereinbelow; and

[0076] a means of display 13 which is connected by a link 14 to thecentral unit 11 and which is able to display, if appropriate, on atleast one display device, in particular a standard display screen 15,mounted in the cockpit of the aircraft, a failure cue relating to atleast one of said pressure sensors 5 (therefore corresponding to afailure cue relating to said air data system 2).

[0077] According to the invention, said central unit 11 comprises, asrepresented in FIG. 2:

[0078] data acquisition means 16 that are connected (links 12) to thetwo pressure sensors 5 of FIG. 1 and that carry out the acquisition offirst and second pressure values relating to the measurements made bysaid two pressure sensors 5 respectively;

[0079] a means of calculation 17 that is connected by links 18 to saiddata acquisition means 16 and that calculates the deviation between saidfirst and second pressure values;

[0080] a means of comparison 19A that compares this deviation receivedvia a link 20 with a recorded predetermined threshold value, for example30 mbar; and

[0081] a means of selection 21A that outputs (or otherwise) an order todisplay a failure cue (which order is transmitted to the display means13 by the link 14), as a function of the result (received via a link22A) of this comparison. More precisely, it outputs a display order ifsaid deviation is greater than said threshold value and it outputs noorder in the converse case.

[0082] Thus, by virtue of the device 1, any failure of a pressure sensor5 of an air data system 2 can be rapidly and reliably detected, withoutcalling upon information external to this air data system 2, such as forexample information output by other air data systems of the aircraft.This therefore makes it possible, should a plurality of air data systemsbe present on the aircraft, to guarantee the strict mutual independenceof the various air data systems.

[0083] In a preferred implementation, the two (or at least two) pressuresensors 5 of the air data system 2 are mounted on either side of thelongitudinal axis 23 of the fuselage 3 of the aircraft, as representedin FIG. 1.

[0084] In a particular implementation, the device 1 moreover comprises,as represented in FIG. 2:

[0085] a standard means 24 for measuring the speed of the aircraftrelative to the air so as to obtain an air speed value; and

[0086] a means 25 which is connected by a link 26 to the means 24 forcomparing the air speed value thus measured with a predetermined speedthreshold, for example 25 m/s (around 50 knots).

[0087] In this case, the means of selection 21A which is connected by alink 27 to the means 25 orders the displaying of a failure cue only if,in addition to the aforesaid conditions, said air speed value is greaterthan said speed threshold.

[0088] In another implementation, the device 1 comprises at least threepressure sensors 5 and the calculation unit 11 comprises as many (three,four, etc.) means of acquisition 16 (FIG. 3) as there are pressuresensors 5.

[0089] In this case:

[0090] the means of calculation 17 calculates all the possibledeviations between the various pressure values taken pairwise;

[0091] the means of comparison 19A compares all the deviations thuscalculated with said threshold value; and

[0092] the means of selection 21A orders a possible displaying of afailure cue, as a function of the various comparisons thus carried out.

[0093] More precisely, said means of selection 21A orders the displayingof a failure cue:

[0094] in a first variant, if at least one of said deviations is greaterthan said threshold value; and

[0095] in a second variant, if all said deviations are greater than saidthreshold value.

[0096] The device 1 can also comprise a means of calculation 28 and amemory 29 that are connected (links 30 to 32) between a means ofacquisition 16 and the means of comparison 19B, as represented in FIG.4.

[0097] In this case, the device 1 can employ the following process:

[0098] B1) make pressure measurements with the aid of at least onepressure sensor 5 of the air data system 2, on the aircraft which is onthe ground and the cabin of which is not pressurized, so as to obtain athird pressure value;

[0099] B2) on the basis of this third pressure value, calculate a firstaltitude corresponding to the ground altitude;

[0100] B3) pressurize the cabin (cockpit and passenger cabin) of theaircraft;

[0101] B4) make the aircraft take off;

[0102] B5) at an instant t0 corresponding to a predetermined time Tafter takeoff, make pressure measurements with the aid of said pressuresensor 5 so as to obtain a fourth pressure value;

[0103] B6) on the basis of this fourth pressure value, calculate asecond altitude corresponding to the aircraft's altitude at saidpredetermined time T after takeoff (that is to say at said instant t0);

[0104] B7) calculate a third altitude corresponding to the aircraft'saltitude with respect to the ground, from said first and secondaltitudes;

[0105] B8) compare said third altitude with a predetermined altitudethreshold; and

[0106] B9) if said third altitude is less than said predeterminedaltitude threshold, order the displaying of a failure cue relating tosaid air data system 2 on the display device 15.

[0107] Preferably, said altitude threshold is less than the altitudereached by the aircraft, at said predetermined time after takeoff,should there be a fault with an engine of the aircraft (which is, inthis case, fitted with at least two engines).

[0108] By way of illustration, said predetermined time T after takeoffcan be substantially equal to 30 seconds, and said altitude thresholdcan be substantially equal to 30 meters (around 100 feet).

[0109] The device 1 can also comprise standard means 33 for monitoringthe engines of the aircraft. These means 33 are connected to the meansof selection 21B by a link 34 so as to inform it of any detection of amalfunction of at least one of the engines of the aircraft. In thiscase, when a failure of a pressure sensor 5 is discerned, the means ofselection 21B orders the displaying of a failure cue only if nomalfunction of an engine is signaled at the same time by the means 33.

[0110] It will be noted that the elements 19B, 21B and 22B of FIG. 4 cancorrespond to the elements 19A, 21A and 22A of FIGS. 2 and 3. However,they may also be means separate from said central unit 11.

[0111] The mode of implementation of FIG. 4 has the advantage ofallowing the detection of the failure of two pressure sensors 5 of thesame air data system 2. For this purpose, it can comprise additionalelements 16, 28 and 29, as is illustrated by broken lines.

[0112] According to the invention, at least one detector 35 which isable to detect a failed coupling between the corresponding pressuresensor 5 and the probe 4 which is associated with this pressure sensor 5can also be provided on at least some of the pressure sensors 5 (FIGS. 1and 5).

[0113] In this case, the central unit 11 moreover comprises, as isrepresented in FIG. 5:

[0114] data acquisition means 36 that are connected by links 37 to saiddetectors 35 and that carry out the acquisition on the ground, beforetakeoff, of information relating to the coupling, which originates fromsaid detectors 35; and

[0115] a means of selection 21C which is connected by links 38 to saiddata acquisition means 36 and which orders, if at least one of saiddetectors 35 signals a failed coupling, the displaying of a failure cuerelating to the air data system 2 on said display device 15.

[0116] In a preferred implementation, at least one of said detectors 35is integrated into a pneumatic connector 7 intended to join a pneumatictube 6 associated with a probe 4 to the corresponding pressure sensor 5.A detector 35 can in particular be a switch actuated by the coupling ofthe connector 7, a laser diode, etc.

[0117] Furthermore, the means of selection 21C can represent the meansof selection 21A and/or the means of selection 21B, or else beindependent of them.

1. A process for detecting the failure of a pressure sensor (5) of anair data system (2) of an aircraft, which comprises at least twopressure sensors (5), wherein at least the following first series ofsteps is carried out: A1) pressure measurements are made with the aid ofsaid two pressure sensors (5) so as to obtain, respectively, first andsecond pressure values; A2) the deviation between said first and secondpressure values is calculated; A3) this deviation is compared with apredetermined threshold value; and A4) if said deviation is greater thansaid threshold value, a failure cue relating to said air data system (2)is displayed on a display device (15) which is mounted on said aircraft:2. The process as claimed in claim 1, wherein the following steps aremoreover carried out: the speed of the aircraft relative to the air ismeasured in such a way as to obtain an air speed value; the air speedvalue thus measured is compared with a predetermined speed threshold;and a failure cue is displayed in step A4), only if said air speed valueis greater than said speed threshold.
 3. The process as claimed in claim2, wherein said speed threshold is substantially equal to 25 m/s.
 4. Theprocess as claimed in claim 1, wherein said threshold value issubstantially equal to 30 mbar.
 5. The process as claimed in claim 1,wherein said two pressure sensors (5) are mounted on either side of thelongitudinal axis (23) of the aircraft, on the fuselage (3) of thelatter.
 6. The process as claimed in claim 1, wherein at least threepressure sensors (5) are provided for said air data system (2), whereinin step A1), pressure measurements are made with the aid of said threepressure sensors (5), wherein in step A2), all the possible deviationsbetween the various pressure values taken pairwise are calculated,wherein in step A3), all the deviations thus calculated are comparedwith said threshold value, and wherein in step A4), a failure cue is oris not displayed depending on the various comparisons thus carried out.7. The process as claimed in claim 6, wherein in step A4), a failure cueis displayed if at least one of said deviations is greater than saidthreshold value.
 8. The process as claimed in claim 6, wherein in stepA4), a failure cue is displayed only if all said deviations are greaterthan said threshold value.
 9. The process as claimed in claim 1, whereinat least the following second series of steps is moreover carried out:b1) pressure measurements are made with the aid of at least one pressuresensor (5) of the air data system (2), on the aircraft which is on theground and the cabin of which is not pressurized, so as to obtain athird pressure value; B2) on the basis of this third pressure value, afirst altitude corresponding to the ground altitude is calculated; B3)the cabin of the aircraft is pressurized; B4) the aircraft is made totake off; B5) at a predetermined time after takeoff, pressuremeasurements are made with the aid of said pressure sensor (5) so as toobtain a fourth pressure value; B6) on the basis of this fourth pressurevalue, a second altitude corresponding to the aircraft's altitude iscalculated; B7) a third altitude corresponding to the aircraft'saltitude with respect to the ground is calculated, from said first andsecond altitudes; B8) said third altitude is compared with apredetermined altitude threshold; and B9) if said third altitude is lessthan said predetermined altitude threshold, a failure cue relating tosaid air data system (2) is displayed on a display device (15) which ismounted on said aircraft.
 10. The process as claimed in claim 9,wherein, in the case of an aircraft fitted with at least two engines,said altitude threshold is less than the altitude reached by theaircraft, at said predetermined time after takeoff, should there be afault with at least one of said engines.
 11. The process as claimed inclaim 10, wherein said predetermined time after takeoff is substantiallyequal to 30 seconds, and wherein said altitude threshold issubstantially equal to 30 meters.
 12. The process as claimed in claim 9,wherein the following steps are moreover carried out: the operation ofthe engines of the aircraft is monitored; and when a malfunction of atleast one of the engines of the aircraft is detected, a failure cue isnot displayed if appropriate in step B9).
 13. The process as claimed inclaim 1, wherein at least the following third series of steps ismoreover carried out: C1) at least one detector (35) which is able todetect a failed coupling between the corresponding pressure sensor (5)and a probe (4) of the air data system (2), which is associated withthis pressure sensor (5), is provided on at least some of the pressuresensors (5); C2) the acquisition on the ground, before takeoff, of cuesrelating to said coupling, which emanate from said detectors (35), iscarried out; and C3) if at least one of said detectors (35) signals afailed coupling, a failure cue relating to said air data system (2) isdisplayed on a display device (15) which is mounted on the aircraft. 14.The process as claimed in claim 13, wherein at least one of saiddetectors (35) is integrated into a pneumatic connector (7) intended tojoin a pneumatic tube (6) associated with a probe (4) to thecorresponding pressure sensor (5).
 15. A device intended for theimplementation of the process specified under claim 1, to detect thefailure of a pressure sensor (5) of an air data system (2) of anaircraft, which comprises at least two pressure sensors (5), whichcomprises: means (16) for acquiring the values of measurements made bysaid pressure sensors (5); means of calculation (17, 28); means ofcomparison (19A, 19B); means of selection (21A, 21B, 21C); and means ofdisplay (13) able to display, on at least one display device (15) whichis mounted on said aircraft, a failure cue relating to said air datasystem (2).